Attempting to set gains with DMM, but can't reach desired voltage...

[JohnKimble]

Your math is correct. If you do the things we talked about here and you still cannot get the amp to produce 31 volts, you can turn the bass boost knob up to about half way and then set the gain. That's not the norm but it's also safe to do in most cases.
But again... try what we talked about first. After all, you were trying to achieve an output from a 60Hz tone while at the same time having the crossover set to block all frequencies above ~40Hz. It stands to reason you could barely get a reading. ;-)

That makes sense. Thanks again for the help, as I am still very very new to all of this. I will report back tomorrow once I've set the gain.

 

[Side Show 10+ year member]

cheers bbeljefe

 

[n2audio 5,000+ posts]

Obviously the initial crossover setting was an issue, but I'm also concerned about the remote bass control.

I would remove that from the equation while setting the gain.

That should allow you to get your 31v measurement.

THEN hook up the remote and see what you get.

Some bass remote's are really just remote gains, and I know there are some amps where the remote gain doesn't do anything unless the amp's gain is maxed. If that's the case - I wouldn't use the remote because effectively, you'd have a sub blower at your fingertips (or anyone else's fingertips that grabbed a hold of it.

 

[JohnKimble]

Well I tried it again with the 40hz -10db tone. With my low pass filter maxed (250hz), and all other settings at 0, I set my head unit to 75% of the maximum volume. The bass remote made no difference if it was connected or not, so I left it connected and maxed. After slowly turning my gain up at the amp itself, I discovered the maximum voltage I could obtain was 19v. It's not until I placed my bass boost in the middle (+6db) that I could reach 31v. I decided to play around with some of the head unit settings.

I left all values of the head unit at 0, with the exception of the subwoofer setting, which I maxed out (+8).

With the subwoofer setting of the head unit at +8, I could easily reach 31v without having to use the bass boost on the amp (left at 0).

Is there a better or more preferred way of the two I have done to obtain 31v?

1): All head unit settings at 0, amp bass boost at +6db, and gain adjusted to 31v.

2): Head unit subwoofer setting at +8, amp bass boost at 0db, and gain adjusted to 31v.

 

[Jeffdachef 5,000+ posts]

may i ask what amp make and model you are using OP?

 

[jrdnhsnbrg 10+ year member]

Keep bass boost off and have the head unit bass setting all the way up, AKA option 2

 

[Jeffdachef 5,000+ posts]

i have a feeling either his particular amp cant really make its claimed power or his headunit's preout voltage is not strong enough.

 

[T3mpest 10+ year member]

No way the HU preout isnt' strong enough. Most amps go down to less than a volt of input voltage to make max output. The issue most likely is his HU is designed to really only put out max voltage on the sub RCA when the subwoofer knob is maxed out. That's the case on most alpine units for example. He just needs to set his gains with his subwoofer volume all the way up, no big deal. Cut it down lower when he wants less bass.

 

[Side Show 10+ year member]

yes option 2

 

[hispls 5,000+ posts]

No way the HU preout isnt' strong enough. Most amps go down to less than a volt of input voltage to make max output. The issue most likely is his HU is designed to really only put out max voltage on the sub RCA when the subwoofer knob is maxed out. That's the case on most alpine units for example. He just needs to set his gains with his subwoofer volume all the way up, no big deal. Cut it down lower when he wants less bass.

This seems likely. Also most head units today can be run to say 30 out of 35 or 27 out of 30 without clipping. Don't be afraid to go up to 85-90% volume with bass boost OFF and subwoofer level at 0dB and see if you can get the same effect. Assuming you have amped mids and highs adjust your gain accordingly.... if you're running them off HU power you'll have to use the subwoofer out level to match.

 

[JohnKimble]

I am running a Kenwood KDC-X597 head unit with 4v preamp, Precision Power PPI BK650.1D mono amp, Bravox PXW12D-2 12" subwoofer, MB Quart DSC 480 4 channel amp with Polk DB6501's up front.

 

[T3mpest 10+ year member]

I am running a Kenwood KDC-X597 head unit with 4v preamp, Precision Power PPI BK650.1D mono amp, Bravox PXW12D-2 12" subwoofer, MB Quart DSC 480 4 channel amp with Polk DB6501's up front.

Sounds good. I'd get a -6db tone and set your gains with that. Gain setting really isn't a science, it's more of an art, IMO. Get your desired voltage from the DMM and then test it on some music. Make sure that you get the bass you expect on the heavy tracks and your clipping at that gain should be minimal on most music and safe for the equipment

 

[vetkilr 10+ year member]

Well I tried it again with the 40hz -10db tone. With my low pass filter maxed (250hz), and all other settings at 0, I set my head unit to 75% of the maximum volume. The bass remote made no difference if it was connected or not, so I left it connected and maxed. After slowly turning my gain up at the amp itself, I discovered the maximum voltage I could obtain was 19v. It's not until I placed my bass boost in the middle (+6db) that I could reach 31v. I decided to play around with some of the head unit settings.  

I left all values of the head unit at 0, with the exception of the subwoofer setting, which I maxed out (+8).

 

With the subwoofer setting of the head unit at +8, I could easily reach 31v without having to use the bass boost on the amp (left at 0).

 

Is there a better or more preferred way of the two I have done to obtain 31v?

 

1): All head unit settings at 0, amp bass boost at +6db, and gain adjusted to 31v.

2): Head unit subwoofer setting at +8, amp bass boost at 0db, and gain adjusted to 31v.

Read the two Bold items. You are essentially defeating yourself. -10db tone makes it quieter(less voltage output), while the +8db sub output boost is almost getting you right back to a 0 DB tone setting.

Most head-units are clean above 75% output nowadays. mine is clean on 47 out of 50 volume wise. I would set gains with a DD-1 or Oscope if it was me.

Any reason why you are trying to get a certain voltage on a -10 db tone?

 

[bbeljefe]

Head unit subwoofer controls don't boost the bass signal, they attenuate it. It may read -8 to +8 but electrically, it's -XdB to 0dB. Alpine designates sub out as 0 to 15 and Pioneer calls it -6 to +6 but those are just labels on the display.

The subwoofer output should be flat when setting gains, regardless the test track's recording level.

 

[JohnKimble]

Read the two Bold items. You are essentially defeating yourself. -10db tone makes it quieter(less voltage output), while the +8db sub output boost is almost getting you right back to a 0 DB tone setting.Most head-units are clean above 75% output nowadays. mine is clean on 47 out of 50 volume wise. I would set gains with a DD-1 or Oscope if it was me.

Any reason why you are trying to get a certain voltage on a -10 db tone?

I am trying to obtain that certain voltage on that -10db tone from what was recommended to me in the thread. Honestly I know very little regarding car stereo.

The head unit does not display +8db, it just says +8.

All I know is that I've read to set the gains with a DMM, I take the lower of the two wattage (amp output or subwoofer) and multiply it by the resistance, and square it to obtain a number in vac to which I would attempt to reach while setting my gain.

240x4 = 960. Sqrt of 960 = 30.98.

Now in regards to -10db, -5db, 0db...I don't know. I have no idea what differences would be achieved by using a -10db tone or a 0db tone, except for minimal risk of clipping using a 0db tone. I read using a 40, 50 or 60hz test tone is recommended for setting my mono amps gains...-10db was recommended so thats what I went with.